1. Field of the Invention
The present invention relates to a testing apparatus, and more particularly, to an apparatus and a method for testing a liquid crystal display panel. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for providing high reliability in testing a unit liquid crystal display panel.
2. Discussion of the Related Art
A liquid crystal display device provides liquid crystal cells arranged in a matrix form with corresponding data signals according to image information respectively to display a demanded image by controlling a light-transmittance of each liquid crystal cells. In order to improve yield, a method of fabricating the liquid crystal display device includes the steps of forming thin film transistor array substrates on a wide mother substrate, forming color filter substrates on the other mother substrate, bonding both of the mother substrates to each other to form a plurality of liquid crystal display panels at the same time. Hence, the method demands a process of cutting the bonded mother substrates into unit liquid crystal display panels.
Such a cutting process of the unit panels generally includes forming a scribing line on a mother substrate using a pen having hardness greater than that of glass, and a process of propagating a crack along the scribing line. Such a cutting process of the unit panels is explained in detail by referring to the attached drawings as follows.
FIG. 1 illustrates a schematic layout of a related art unit liquid crystal display panel prepared by bonding a thin film transistor array substrate and a color filter substrate to each other.
Referring to FIG. 1, a liquid crystal display panel 10 includes an image display part 13 having liquid crystal cells arranged in a matrix form, a gate pad part 14 connected to gate lines of the image display part 13, and a data pad part 15 connected to data lines. In this case, the gate and data pad parts 14 and 15 are respectively formed on the edge areas of a thin film transistor array substrate 1 which does not overlap a color filter substrate 2. The gate pad part 14 provides the gate lines of the image display part 13 with each corresponding scan signals supplied from a gate driver integrated circuit, and the data pad part 15 provides the data lines with image information supplied from a data driver integrated circuit.
On the thin film transistor array substrate 1 of the image display unit 13, the data lines having the image information applied thereto and the gate lines having the scan signals applied thereto to cross vertically with each other. Thin film transistors at each intersection are formed to switch the liquid crystal cells. Pixel electrodes are connected to the thin film transistors to drive the liquid crystal cells. A passivation layer is formed on the entire surface to protect the electrodes and the thin film transistors.
Moreover, color filters separated by a black matrix for each cell area are formed on the color filter substrate 2. A transparent common electrode as a counter electrode of the pixel electrode is formed on the thin film transistor array substrate 1.
A cell gap is provided between the thin film array substrate 1 and the color filter substrate 2, which are bonded to each other by a sealing part (not shown) formed at the periphery of the image display unit 13, so as to be spaced apart from each other. And, a liquid crystal layer (not shown) is formed in the space between the thin film transistor array substrate 1 and the color filter substrate 2.
FIG. 2 illustrates a cross-sectional view of a first mother substrate having thin film transistor array substrates 1 and a second mother substrate having color filter substrates 2, in which the first and second mother substrates are bonded to each other to form a plurality of liquid crystal display panels.
Referring to FIG. 2, each unit liquid crystal display panel has a thin film transistor array substrate longer than a corresponding color filter substrate 2. This is because the gate and data pad parts 14 and 15 are formed at the corresponding edges of the thin film transistor array substrate 1 which does not overlap the color filter substrate 2, as shown in FIG. 1.
Hence, the second mother substrate 30 and the color filter substrates 2 formed thereon are spaced apart from each other by a dummy area 31 corresponding to the protruding area of each thin film transistor array substrate 1 on the first mother substrate 20.
Moreover, the unit liquid crystal display panels are arranged properly to make best use of the first and second mother substrates 20 and 30. Although it depends on models, the unit liquid crystal display panel is generally spaced apart from each other at a distance corresponding to the area of the other dummy area 32.
After the first mother substrate 20 having the thin film transistor array substrates 1 is bonded to the second mother substrate 30 having the color filter substrates 2, the liquid crystal display panels are individually cut. In this case, the dummy area 31 of each color filter substrate 2 of the second mother substrate 30 and the other dummy area 32 separating the unit liquid crystal display panels from each other are removed at the same time.
FIG. 3 illustrates a layout of a related art apparatus for testing a unit liquid crystal display panel. As shown in FIG. 3, the related art apparatus for testing a unit liquid crystal display panel includes first and second test bars 101 and 102 for testing cutting states and corresponding to two longer sides (i.e., a side having a data pad part and its confronting side) of a unit liquid crystal display panel 100, and third and fourth test bars 103 and 104 for testing cutting states and corresponding to two shorter sides (i.e., a side having a gate pad part and its confronting side) of a unit liquid crystal display panel 100.
The first and second test bars 101 and 102 are to inspect whether a burr remains on the longer sides of the unit liquid crystal display panel 100 cut by a touching method. The third and fourth test bars 103 and 104 are to inspect whether a burr remains on the shorter sides of the unit liquid crystal display panel 100 cut by the same method for cutting the longer sides of the unit liquid crystal display panel 100.
Meanwhile, since the unit liquid crystal display panel 100 differs in size in accordance with a model, the first and second test bars 101 and 102 and the third and fourth test bars 103 and 104 are prepared to have the same lengths of the longer and shorter sides of the largest model of the unit liquid crystal display panel 100 for inspecting whether a burr remains on the longer and shorter sides of any kind of the unit liquid crystal display panel 100.
Moreover, in the unit liquid crystal display panel 100, a color filter substrate 120 is bonded to a thin film transistor array substrate 110 so that one side of the thin film transistor array substrate 110 protrudes from the corresponding color filter substrate 120. As described with reference to FIG. 1, the gate and data pad parts are formed at the corresponding edges of the thin film transistor array substrate 110 that does not overlap the color filter substrate 120.
Hence, a step difference is generated at each side of the longer and shorter sides of the unit liquid crystal display panel 100. In order to inspect the longer side of the unit liquid crystal display panel 100, the first test bar 101 corresponding to the longer side of the unit liquid crystal display panel 100 having a data pad part is formed to gear with the longer side of the unit liquid crystal display panel 100 having the step difference. Also, the third test bar 103 corresponding to the shorter side of the unit liquid crystal display panel 100 having a gate pad part is formed to gear with the shorter side of the unit liquid crystal display panel 100 having the step difference.
As described above, an inspection is made to determine whether a burr remains on the longer and shorter sides of the unit liquid crystal display panel 100 by a touching method using the first to fourth test bars 101 to 104. Thereafter, an operator then extracts the unit liquid crystal display panel 100 without a burr from the production line for a period of time to inspect whether a cutting size of the unit liquid crystal display panel 100 is proper or not through an additional measurement apparatus.
The related art apparatus and method for testing the liquid crystal display panel art determine whether a burr remains on the longer and shorter sides of the unit liquid crystal display panel by that the first to fourth test bars physically touch the longer and shorter sides of the unit liquid crystal display panel.
However, reliability of the test is low. Also, a burr cannot be detected if the longer and shorter sides of the unit liquid crystal display panel are torn in part to form a groove or a recess.
In the related art apparatus and method for testing the liquid crystal display panel, the unit liquid crystal display panel that passed the inspection is extracted from the production line for a period of time to carry out the size test of the cut unit liquid crystal display panel through an additional measurement apparatus. Hence, an operator transports the unit liquid crystal display panel from the production line to the measurement apparatus for the size test of the cut liquid crystal display panel and then carries out the size test in the measurement apparatus. Such a work is troublesome as well as inconvenient. Besides, since the time taken for the size test of the cut unit liquid crystal display panel is increased, and productivity becomes decreased.
Moreover, as an expensive measurement apparatus is necessary in addition, the equipment and maintenance costs of the production line are increased, thereby inevitably increasing a product cost.
Finally, since the size test is a sampling test for a period of time, reliability of the test is low. If a remaining burr is spotted on the liquid crystal display panel, the whole operation is stopped and then all the unit liquid crystal display panels after the previously sampled unit liquid crystal display panel should be inspected. In such a case, the unit liquid crystal panels on which the subsequent processes are already carried out may be a waste of raw materials and time.